This is a multidisciplinary, four-year progressive study of the transmission and natural history of human herpesvirus 8/Kaposi's sarcoma-associated herpesvirus (HHV-8/KSHV) in 500 men. The intent of the study is to: identify biological and behavioral risk factors for acquisition of HHV-8/KSHV infection; and describe patterns of HHV-8/KSHV virologic activity, including types of host immunologic response and the relationship of virologic activity and host response to the development of Kaposi's sarcoma. The GCRC provides outpatient rooms, the nursing staff assists in collection of blood specimens, and the dietary staff provides light snacks for the 3 hour visits.